High vacuum gate valve having improved metal vacuum seal joint

ABSTRACT

A two part high vacuum gate valve construction includes a control mechanism part having a limited displacement stem passing through a first generally rectangular high vacuum flange and a valve body part including a generally rectangular case, a second generally rectangular high vacuum joint providing flange having a mirror image sealing geometry to the first high vacuum flange, two machined fluid flow flanges passing through openings defined through opposite sidewalls of said case and sealed thereto, at least one of the fluid flow flanges having an inside gate sealing surface machined prior to insertion through and sealing of the flange to the sidewall of the case; a two part, levered carriage having a central transverse pivot joint and having an endwall engagement mechanism for causing the pivot joint to pivot toward the inside gate sealing surface of the one flow flange in response to continued actuation force supplied by the control stem shaft after an inside endwall of said case has been contacted; a valve gate having a sealing surface for engaging the inside gate sealing surface of the one flow flange when the carriage means is opposite the other flow flange the gate being pivotally attached to the carriage at the central transverse pivot joint, a double jointed linkage assembly having one link part pivotally fixed to the second flange and linked to the control stem shaft for double jointed arcuate movement.

FIELD OF THE INVENTION

The present invention relates to apparatus for handling fuild flow inhigh vacuum operating environments. More particularly, the presentinvention relates to apparatus and methods for improving generallyrectangular metal vacuum joints and providing improved high vacuum gatevalves which incorporate, among other features, the improved jointconstruction and methods of the present invention.

BACKGROUND OF THE INVENTION

High vacuum gate valves are typically employed in extreme environments,such as are encountered in fabrication processes of integrated circuitsemiconductors, for example. Other processes involving technologies suchas low pressure chemical vapor deposition: sputtering, plasma, and thelike, also require high vacuum joints in piping and reliable high vacuumgate valves. Such joints and valves are typically formed of highcorrosion resistance materials such as stainless steel, and they may beadapted for operations at very high temperatures.

High vacuum gate valves typically provide for actuation from theambient, ideally with no loss of vacuum level. Annular metallic sealingsurfaces for such valves have been successfully provided in the past.One such annular sealing surface is illustrated in U.S. Pat. No.3,208,758, a salient feature of which is reproduced herein as FIG. 1.

Annular sealing surfaces, such as the one illustrated by the FIG. 1flange 10, have been found to be readily formable because such surfaces,like the protruding portion 12 of the FIG. 1 flange 10, and the inwardlyadjacent flat portion 14 and outwardly adjacent vertical wall 16thereof, may be created by turning the flange workpiece relative to, andmachining with an appropriate cutting tool or bit of a metal lathe.

Generally rectangular sealing surfaces, such as the one illustrated inFIG. 2 herein, have proven to be very difficult to fabricate with priorart techniques. In FIG. 2 a rectangular flange 20 defines a generallyrectangular sealing surface 22, and the inside peripheral ridge 24 ofwhich forms a twenty degree angle with the plane of the sealing surface22 of the flange 20. The inwardly rising ridge 24 is typically formed byend milling of the flange with a mill. In order to provide the sealingsurface 22 with necessary clearance immediately outside the ridge 24into which the gasket metal will flow under extreme clamping pressure,the prior practice has been to mill perpendicular slots 26, 28 all awayacross the flange, as shown in FIG. 2. The major drawback of thisapproach has been that at the corners 30, where different millingdirections intersect, hand burnishing and polishing has been required inorder to achieve the precision needed to achieve a high vacuum seal. Acold welded rectangular copper wire gasket was placed onto the sealingsurface 24 and was caused to flow throughout the sealing area defined bythe flange 20 and its complementary mating flange by virtue of extremeclamping pressure applied between the two flanges as by multiple bolts.The seals resultant from flanges formed like the flange 20 were notalways reliable, and often developed leaks.

One high vacuum valve construction employing a generally rectangularsealing surface at the gate is depicted in U.S. Pat. No. 3,212,036. Thegenerally rectangular sealing surface of the gate, which engaged a metalgasket material, was formed as a separate element from the gate and wassubsequently welded onto the gate structure. One problem with welding ofparts to the gate element is that it causes the gate to warp or buckleand thereby lose its precisely specified geometry and fail to achieve areliable high vacuum seal.

Another generally rectangular sealing surface employed in the prior artis illustrated in FIG. 3. Therein, a flange 40 includes an inwardlyrising ridge 42 and a very wide recessed sealing surface 44 bounded byan outer wall 46. The width of the surface 44 was required by the factthat the end milling tool used to machine the slanted surface of theprojecting ridge 42 had to clear the top of the wall 46 while theslanted surface. This created a severe problem in that the swagingpressure upon the copper gasket material generated by the ridge 42 asthe flange 40 was clamped to its mating flange, failed to cause thecopper gasket to flow all the way to the back wall 46. This failureresulted in a tendency of this prior joint to develop leaks. Inaddition, the copper gasket had to be formed around bolt openings 48,further increasing the tendency of this prior design to leak.

SUMMARY OF THE PRESENT INVENTION WITH OBJECTS

A first general object of the present invention is to provide agenerally rectangular metal high vacuum joint for a pipe flange, gatevalve, and the like, and method for making the same, which overcomes thelimitations and drawbacks of the prior art.

A second general object of the present invention is to provide a gatevalve of improved design and construction which overcomes limitationsand drawbacks of the prior art by advantageously incorporating theimproved generally rectangular metal high vacuum joint aspect of thepresent invention.

One aspect of the present invention is a flange which provides a highvacuum generally rectangular joint in combination with a second flangeof mirrored geometry and metal gasket compressed and swaged therebetweento achieve a high vacuum seal at the joint. The new flange includes asubstantially planar face, a generally rectangular, continuously formedtrough defined in the face, the trough being substantially semicircularin cross section, and a raised, substantially planar swaging surfacecontinuously formed adjacently inward of and abutting the trough, theswaging surface having an outward upward slope angle with respect to theface.

A related aspect of the invention is the forming method for the flangewhich includes the steps of forming a substantially planar face on theflange, continuously forming a generally rectangular trough in said facehaving a substantially semicircular cross section, and then continuouslyforming a raised, substantially planar swaging surface adjacently inwardof and abutting said trough in a manner by which said swaging surfacehas an upward and outward slope angle with respect to the plane of saidsealing surface.

Another aspect of the present invention provides a two part high vacuumgate valve construction comprising a control mechanism part and a valvebody part.

The control mechanism part includes a stand pipe housing; a linearlytranslatable control stem shaft; a baffle assembly including anexpansible baffle having an accordion pleat baffle for sealing the stemshaft relative to the ambient, the baffle expanding and contractinglongitudinally throughout the limited displacement range of the stemshaft; a first generally rectangular high vacuum joint providing flangeto which the stem pipe housing is mounted and the bonnet is sealed onone major face, and having a central opening through which the shaftfreely passes, and a high vacuum joint providing geometry on the othermajor face thereof enabling the control mechanism part to be removablyjoined to and sealed with the valve body part; and, a displacementmechanism, either manual or automatic, for controllably displacing theshaft.

The valve body part includes a generally rectangular case secured at anupper end to a second generally rectangular high vacuum joint providingflange having a mirror image sealing geometry to the first high vacuumjoint providing flange; two machined fluid flow flanges passing throughopenings defined through opposite sidewalls of the case and sealedthereto, at least one of the fluid flow flanges having an inside gatesealing surface machined prior to insertion through and sealing of theflange to the sidewall of the case, the fluid flow flanges definingcentral flow passages and including outer sealing means enablingformation of high vacuum joints with piping to which the valve may beoperationally attached; a two part, levered carriage having a centraltransverse pivot joint and having endwall engagement means for causingthe pivot joint to pivot toward said inside gate sealing surface of theone flow flange in response to continued actuation force supplied bysaid control stem shaft after an inside endwall of said case has beencontacted; a valve gate having a sealing surface for engaging the insidegate sealing surface of the one flow flange when the carriage means isopposite the other flow flange and having a back surface with a pivotedengagement mechanism, the engagement mechanism engaging the carriage atthe central transverse pivot joint; a double jointed linkage assemblyhaving one line part pivotally fixed to the second flange and liked tothe control stem shaft for double jointed arcuate movement as the stemshaft is moved along its locus of rectilinear limited displacement, andhaving a second link part linked to the first link part and to thecarriage, for levering actuation force supplied by the central stemshaft to the carriage thereby to cause the gate to close and then to beurged against the inside flow flange sealing surface in sealingengagement therewith.

In a further aspect of the present invention a manual displacementmechanism for the stem shaft includes a threaded stem extension and ajournalled threaded rotation shaft are formed with complementary doublethreads, thereby halving the thread pitch per unit measure withoutreduction of mechanical engagement between the stem extension and thejournalled rotation shaft.

In one more aspect of the present invention the double jointed linkageassembly comprises a stop dog formed on one of the one link part andsecond link part, and a stop pin formed on the other of the one linkpart and second link part, the stop dog for engaging the stop pin afterthe one link part and second link part having passed throughlongitudinal alignment to an over-center locking position, forcing thecarriage to bend along its central stem shaft thereby to force the gateinto sealing engagement with the inside sealing surface of the one flowflange.

In yet another aspect of the present invention, the pivoted engagementmechanism on the back surface of the valve gate is formed by the processof lathing two recessed annuli therein so as to define a raised annulusand then by milling off opposed equal length chords of the annulusthereby leaving two raised integral bosses which are pivotally engagedby the central stem shaft of the carriage.

In one more aspect of the present invention the baffle assembly includesa bonnet enclosure, a bushing mounted to the bonnet enclosure forprecisely aligning the stem shaft for limited displacement rectilinearmovement, an expansible baffle having an accordion pleat baffle with aninterior space communicating with the ambient and an exterior space, thebaffle having one end sealed to an inside end wall of the bonnet andhaving another end sealed to an annulus formed on the stem shaft, thebaffle expanding and contracting longitudinally throughout the limiteddisplacement range of the stem shaft.

These and other objects, advantages and features of the presentinvention will become even more apparent upon considering the followingdetailed description of preferred embodiments, presented in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 is an enlarged corner portion sectional view of a flanged annularmetal vacuum joint in accordance with the prior art.

FIG. 2 is a top plan view of a prior art rectangular metal vacuum jointmachined in accordance with the FIG. 1 section.

FIG. 3 is an enlarged corner portion sectional view of a flangedgenerally rectangular metal vacuum joint proposed in the prior art.

FIG. 4 is a top plan view of a flange defining a generally rectangularmetal high vacuum joining surface in accordance with principles of thepresent invention.

FIG. 5 is a view in elevation and section of the flange depicted in FIG.4 taken along the line 5--5 therein.

FIG. 6 is an enlarged sectional view of a generally rectangular metalhigh vacuum joint in accordance with principles of the presentinvention, formed by the joining surface depicted in FIG. 4, by anoppositely facing, symmetrical joining surface of a second flangeclamped to the first flange, and by a ductile, flowable gasket metalswaged by the compression of the two flanges together so as to flow intoand occupy a sealing space defined thereby.

FIG. 7 is an isometric view of a high vacuum gate valve incorporatingthe principles of the present invention, including the generallyrectangular metal high vacuum joint depicted in FIG. 6.

FIG. 8A is an isometric exploded assembly drawing of a manually operatedcontrol portion of the high vacuum gate valve depicted in FIG. 7,illustrating the components thereof.

FIG. 8B is an isometric exploded assembly drawing of a control portionof the high vacuum gate valve depicted in FIG. 7 and capable ofautomatic operation by a controlled electropneumatic actuator assembly.

FIG. 9 is an isometric exploded assembly drawing of a base portion ofthe high vacuum gate valve depicted in FIG. 7, illustrating thecomponents thereof.

FIG. 10 is a top plan view in section of a unitary gate element of thehigh vacuum gate valve portion depicted in FIG. 9, taken along the line10--10 therein and formed in accordance with one aspect of the presentinvention.

FIG. 11 is a back view in elevation of the gate valve depicted in FIG.10 illustrating by broken lines the fabrication process yielding aunitary gate valve element.

FIG. 12 is a diagrammatic view in front elevation and section of thebase portion of the high vacuum gate valve depicted in FIG. 7, showingthe gate element in a fully retracted or "valve-open" position.

FIG. 13 is a diagrammatic view in right side elevation relative to theFIG. 12 view of the gate valve depicted in FIG. 7 showing the gateelement in the fully retracted position illustrated in FIG. 12.

FIG. 14 is similar to the FIG. 12 view and shows the gate element is ahalf closed position relative to the base.

FIG. 15 is similar to the FIG. 13 view and shows the gate element in thehalf closed position depicted in FIG. 13.

FIG. 16 is similar to the FIG. 12 view and shows the gate element in aclosed, but not yet locked, position.

FIG. 17 is similar to the FIG. 13 view and shows the gate element in aclosed, but not yet locked, position.

FIG. 18 is similar to the FIG. 16 view and shows the gate element in aclosed, locked and sealing position.

FIG. 19 is similar to the FIG. 17 view and shows the gate element lockedagainst its sealing surface as the control linkage assembly becomeslocked against a locking position in accordance with a further aspect ofthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS High Vacuum GenerallyRectangular Metal Joint 50

An improved high vacuum generally rectangular metal joint 50 isillustrated in FIGS. 4, 5 and 6. Therein, a rectangular flange 52defines a generally rectangular central opening 54 e.g. in order toaccomodate linkage apparatus for a high vacuum gate valve 100 to bedescribed and explained hereinafter. The flange 52 includes acontinuously formed, outwardly and upwardly sloping, ridge portion 56immediately outwardly adjacent to the central opening 54. Outside of theridge portion 56, an annular well 58 is continuously formed. The ridgeportion 56 and the annular well 58 are each formed by automatic CNCmilling operations and are therefore very precise. Since the directionof slope of the ridge portion 56 is outward (as opposed to inward slopeof the prior art ridge illustrated in FIG. 3, for example), there is noneed to allow for clearance for the end milling tool bit relative to theflange 52.

Suitable clamp bolt holes 60 are defined through the flange 52 atsuitable intervals. Narrow, shallow slots 62, 64 are also formed throughopposite minor dimension ends of the flange, and these slots enablegases otherwise entrained in the well 56 to escape when the flange 52 isclamped to a mirror image flange, such as the flange 66 depicted in FIG.6 by bolts 68 which have threads engaging inside threads formed in holes70 in the flange 66, for example.

A suitable continuous metallic gasket 72, such as a stamped, generallyrectangular copper sheet gasket, e.g. approximately 0.080" thick, isplaced between the two flanges 52 and 66 before they are clampedtogether by the bolts 68. This soft metal gasket is swaged by theopposed ridges 56 and 74, and flows into and occupies the entire volumedefined by the wells 58 and 76, of the flanges 52 and 66. The result,illustrated in FIG. 6, is an easily formed high vacuum metal joint 50which does not leak.

High Vacuum Gate Valve 100

The joint 50 is preferably included as an important structural elementof the improved high vacuum gate valve 100 illustrated in FIG. 7.Basically, the valve 100 is formed of two parts or sections, a controlmechanism 102 and a valve body section 104. The structural elementsmaking up a manual control mechanism section 102 are illustrated anddiscussed in connection with FIG. 8A, while the structural elementscomprising an electropneumatic automatic control mechanism 103 areillustrated and discussed in connection with FIG. 8B. The same referencenumerals are used in FIGS. 8A and 8B for the same structural elements.The structural elements making up the valve body section 104 areillustrated and discussed in connection with FIG. 9. The two sections102 (or 103) and 104 are joined together at a non-leak joint previouslydescribed herein by the flanges 66 and 52 respectively.

Manual Control Mechanism 102 (FIG. 8A)

Turning now to the manual control mechanism 102 depicted in FIG. 8A, abellows assembly 106 is formed on the flange 66, and the assembly 106includes a central stem 108, an annular disk 110 continuously welded tothe stem 108 at a central opening therethrough. A bellows element 112 issealed at a lower end thereof to the outer periphery of the disk 110. Agenerally tubular bonnet 114 shrouds the bellows 112 and stem 108, andit is sealed to the flange 66 in an airtight arrangement, as by acontinuous annular weld. The bellows is secured to, and sealed at theinside of a top end wall of the bonnet 108, so that the inside spacedefined by the bellows is at ambient air pressure, while the outside ofthe bellows may be at a high vacuum. The bonnet 114 is sized so that thestem 108 and attached bellows 112 are free to move in the inside spacedefined thereby without restriction, while providing a reliable vacuumbarrier between the control mechanism and the interior space of thevalve body mechanism 104.

In accordance with an important feature of the present invention, anelongated bronze bushing 116 is secured through a central opening of athickened top endwall portion 118 of the bonnet 114 by two bushingretaining rings 120, 122. Unlike prior art bellows assemblies, such asthe type illustrated in the referenced U.S. Pat. No. 3,212,036, theelongated bushing 116 guides the central stem 108 precisely along itsaxis of lineal movement and thereby minimizes lateral movements of thebellows 112 which otherwise increase metal fatigue and failure.

In another aspect of the present invention, a double Acme standardthreaded stem extension 124 is secured to the central stem 108 by arecessed pin 126. Each of the two equally-spaced-apart helixes formingthe threads on the extension 124 has a pitch of approximately five turnsper inch. By using a pair of helical threads, a substantial mechanicalengagement is achieved between the threads of the extension 124 andinside threads of a bearing shaft 128; at the same time, the manualcontrol section 102 requires but about six turns to move a gate of thevalve 100 from a fully open position (FIGS. 12 and 13) to a fully closedand locked position (FIGS. 18 and 19). In many industrial processes, itis essential that the valve 100 be capable of rapid, yet preciseactuation, and the use of the double threads achieves this result.

In fabricating the double threads on an engine lathe, the first helicalthread is machined. Then, the gears driving the lead screw of the latheare disengaged, and the lead screw drive gear is rotated manually 180degrees and reengaged. This places the cutting tool forming the threadsexactly between the first thread formed, and the second thread (both onthe extension 124 and inside the bearing shaft 128 may now be cut.

A double flanged stand pipe assembly 130 includes a lower flange 132which is mounted flush to the top surface of the flange 66 by the bolts68. Transverse holes 134 through the lower flange 132 align with theholes 70 of the flange 66. In the valve (unlike the arrangement shown inFIG. 6, the holes 60 through the lower main flange 52 are threaded tomate with the threads of the bolts 68. A cylindrical tube 136 is securedat one end to the lower flange 132 and at an upper end to an annularupper flange 138. The flange 138 has holes 140 defined therethrough forfreely receiving bearing housing bolts 142. The bolts thread intoaligned, threaded holes defined in a lower annular portion of a bearinghousing 144 and thereby secure it to the stand pipe assembly 130.

The bearing shaft 128 rotates freely in the bearing housing 144. Anupper bearing assembly includes an upper axial bearing 146 and twobearing washers 148 and 150 which separate a upper thrust bearing 152.In similar fashion, a lower bearing assembly includes a lower axialbearing 154 and two bearing washers 156 and 158 which separate a lowerthrust bearing 160. An outer lower end portion of the cylindricalbearing housing 144 is provided with threads 162, and these threads areengaged by two locking nuts 164, 166, after the bearing shaft 128 isassembled with the upper and lower bearing assemblies in the bearinghousing 144.

A knob 168 is secured by a setscrew 170 to the upper end of the bearingshaft 128 to facilitate manual actuation of the valve 100. As the knob168 is rotated, the stem extension 124 and central stem 108 moveaxially.

Automatic Electropneumatic Control 103

The automatic electropneumatic control assembly 103 is depicted in FIG.8B. Therein, a pneumatic stem extension 170 is attached to the centralstem 108 by the recessed pin 126. An air cylinder body 172 is attachedto the upper flange 138 of the stand pipe assembly 130 by the bolts 142.

An electrical solenoid 174 operates a valve 176 which operates apneumatic piston 177 slidably disposed inside the body 172. Air lines178, 180 extend to fittings 182, 184 secured through the cylindricalsidewall of the air cylinder body 172 and thereby apply pressurized airsupply to each side of the piston 177, causing the piston 177 to move upor down, depending upon which fitting is receiving pressurized air.

The plunger within the assembly 176 is attached to the pneumatic stemextension 170. An O-ring seal 186 is provided to seal the joint betweenthe pneumatic stem extension 170 and the body 172 so that air pressuredoes not enter the inside of the stand pipe assembly 130. A bolt 188secures the piston 177 to the stem extension 170. A piston O-ring 190 isprovided to seal the outer cylindrical surface of the piston 177relative to the inner cylindrical surface of the body 172. A threadedlid 192, sealed by a gasket 194, mates with threads of and seals off theupper end of the body 172.

In practice the valve assembly 176 is supplied with presurized air,typically at about 20-25 psig air pressure. An air filter/lubricator isrecommended for use in the air supply to ensure trouble free operationof the valve assembly 176 and the piston 177. As the piston 177 moves upor down, so does the central stem 108.

Valve Body Section 104

The valve body section 104 of the high vacuum gate valve 100 is depictedin FIG. 9. Therein, a valve body assembly 200 includes an enclosedrectangular case 202. The case has an open upper end secured and sealedas by an outer peripheral TIG (tungsten in glass) weld to the lowerflange 52. Two cylindrical flanges 204, 206 are secured throughcylindrical openings in opposite walls of the case 202. The flanges 204,206 are machined on both faces, with an interior machined face 208, 210being recessed so as to fit through and extend slightly beyond the case202, as shown for example in FIG. 13. An annular TIG weld 212 securesand seals each flange 204, 206 to the case. This method of fabricationand assembly achieves a very precise sealing surface for a gate element214 without the need to machine the surface inside of the case (anextremely complicated and difficult machine tool set up). Each flange204, 206 is provided with threaded holes 216 and is machined to providea conventional annular metal high vacuum joint of the type discussed inconnection with FIG. 1.

The rectangular cooper seal 72 fits on the sealing surface of the flange52 as previously explained in connection with FIGS. 4-6, and the holes60 of the flange 52 are threaded in the FIG. 9 embodiment, so that thebolts 60 may secure the stand pipe lower flange 132 and the upper flange66 to the flange 52 in the configuration illustrated in FIG. 7.

In one aspect of the present invention, the disk-shaped gate 214 isformed with two integral connecting bosses 218, 220 by machining from asingle cylindrical stainless steel workpiece, as illustrated in FIGS. 10and 11. Annular back portions 222, and 224 of the gate 214 shown bydashed lines in FIG. 10 are cut away by a lathe operation. Then, theremaining raised annular portions 226 and 228 depicted by dashed linesin FIG. 11 are cut off in milling operations, leaving the two bosses218, 220. Axially aligned holes 230 are then drilled transverselythrough the bosses 218, 220 to enable a fore carriage link pin 232 topivotally secure the gate 214 to a fore carriage 234. A metal orelastomer gate o-ring 236 seats in an annular well 238 formed in thesealing surface face 240 of the gate 214.

By forming the gate of a single workpiece, instead of welding bossesonto the back of the gate as was the prior art practice, warpage andmisalignment of the gate relative to a sealing surface 210 is therebyavoided, thereby achieving a much more positive, leak free valve 100than heretofore achieved.

Two carriage wheels 242, 244 are secured to the fore carriage 234 bypins 246, 248 with E-ring locking washers 250, as shown in FIG. 9. Asalready explained, the fore carriage link pin 232 passes through theholes 230 of the gate bosses 218, 220, and it also passes throughaxially aligned openings of the fore carriage 234 and through transverseopenings at one end of each of two carriage-gate links 252, 254. TwoE-ring lock washers 256 secure the pin 232 in place.

The carriage-gate links 252, 254 are pivotally secured to an aftcarriage block 256 by pins 258. Two carriage wheels 260, 262 are securedto the aft carriage block 256 by pins 264, 266 and E-ring lockingwashers 268. A spring 270 centered about the fore carriage link pin 232biases the fore carriage 234 into longitudinal alignment with the aftcarriage 256, and causes the gate 214 to move away from the opposedsealing surfaces 240, 210 of the gate 214 and the flange 206,respectively.

A lower link 272 is transversely pivotally connected at its lower end tothe aft carriage block 256, and at its upper end to a pair of spacedapart, parallel upper links 274, 276. A stem link 278 is pivotallysecured for transverse pivtoal movement between the links 274 and 276.The stem link 278 is slotted at its upper end and pivotally engages thelower end of the central stem 108. An aft carriage link pin 280pivotally secures the stem link 278 and the central stem 108.

A boss 282 secured to the underside of the upper flange provides ananchor for the upper links 274 and 276. A pin 284 passes through eachlink 274, 276 and the boss 282 to enable the links to rotate about theboss in a limited range of arcuate movement. E-ring lock washers 286secure the pins 278 and 284 in place.

A stop dog 288 extends from the upper end of the lower link 272. Thisdog 288, shown in FIG. 12, contacts a stop pin 290 when the links 272and 274-276 are in an "overcenter" locking position as shown in FIG. 18as when the central stem 108 is fully extended.

A carriage assembly 300 includes the wheels 242, 244, 260, 262, the forecarriage 234, the links 252, 254 and the aft carriage 256 and relatedhardware.

Operation of the Valve 100 (FIGS. 12-19)

FIGS. 12 and 13 illustrate the valve-open, gate fully retracted positionof the valve 100. Therein, the central stem 108 has pulled the links278, 274-276 and 272 to the position shown in FIG. 12 with the resultthat the gate carriage assembly 300 has moved on its wheels 242, 244,260, 262 to a fully retracted position, carrying the gate 214 with it.The spring 270 has biased the fore carriage 234 and gate 214 away fromthe gate sealing surface 210 of the flange 206. The wheels 242, 244 arein contact with the interior sidewall of the case 202 opposite thesidewall mounting the flange 206.

In FIGS. 14 and 15, the carriage 300 has moved to an intermediateposition with the passage between the flanges 206 and 204 beingpartially obstructed by the gate 214.

In FIGS. 16 and 17, the carriage 300 has moved the gate into a positioncompletely blocking the passage between the flanges 206 and 204, and thewheels 242, 244 have contacted the bottom wall of the case 202, but thelinks 272, 274-276 and 278 have not yet reached a maximum extension, andthe gate 214 is not sealed against the sealing surface 210.

In FIGS. 18 and 19, the gate 214 has become sealed against the sealingsurface 210 of the flange 206. The carriage 300, unable to movelongitudinally any farther because of the endwall of the case 300, hasmoved transversely by becoming axially shortened by pivoting at the linkpin 232 as shown in FIG. 19. (The fore carriage 234 and the aft carriage256 define a more acute angle facing the flange 204 in the lockingposition.) At the same time, the links 272, 274-276 and 278 have gonebeyond center (or longitudinal alignment of the link 272 with the linkpair 274-276 to a locking position illustrated in FIG. 18 wherein thestop dog 288 has contacted the stop pin 290. In this locking position ofthe valve 100, he beyond or over center position of the links 272 and274-276 automatically causes the gate 214 to remain in a locked andsealed position relative to the sealing surface 210 without need for anyresidual force to be applied by the central stem 108.

To those skilled in the art to which the present invention pertains,many changes in construction and widely varying embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of this invention as more particularlyspecified by the following claims. The disclosures and the desciptionherein are purely illustrative and are not intended in any sense to belimiting of the scope of this invention.

I claim:
 1. A flange for providing a high vacuum generally rectangularjoint in combination with a second flange of mirrored geometry and ametal gasket compressed and swaged therebetween to achieve a high vacuumseal at the joint, the flange comprising a substantially planar face, agenerally rectangular, continuously formed trough defined in said face,said trough being substantially semicircular in cross section, and araised susbtantially planar swaging surface continuously formedadjacently inward of and abutting said trough, said swaging surfacehaving an outward upward slope angle with respect to said face.
 2. Theflange set forth in claim 1 wherein the slope angle of the swagingsurface lies in a range of 10 to 30 degrees with respect to the plane ofthe sealing surface.
 3. A method for forming a flange for achieving agenerally rectangular high vacuum generally rectangular joint incombination with a second flange of mirrored geometry and a metal gasketcompressed and swaged therebetween to achieve a high vacuum seal at thejoint, the forming method comprising the steps of forming asubstantially planar face on the flange, continuously forming agenerally rectangular trough in said face having a substantiallysemicircular cross section, and then continuously forming a raised,substantially planar swaging surface adjacently inward of and abuttingsaid trough in a manner by which said swaging surface has an upward andoutward slope angle with respect to the plane of said sealing surface.4. The method for forming the flange set forth in claim 1 wherein thestep of forming the upward and outward slope angle of the swagingsurface comprises the step of forming the angle in a range of 10 to 30degrees with respect to the plane of the sealing surface.